Non-uniform linear antenna array and broadband direction finding method thereof

Abstract

The invention relates to a non-uniform linear antenna array and a broadband direction finding method thereof, and belongs to the technical field of direction of arrival estimation in electromagnetic signal processing. The invention provides a design mode of a non-uniform array covering a wide-band half-wavelength, so that part of array elements in the array can move, and by means of a virtual array element method, the flexibility of the array and the frequency band range covered by the array are greatly improved. The invention provides a calibration method for solving the phase deviation caused by an antenna pattern and a radio frequency channel, and the deviation caused by the antenna pattern and the radio frequency channel is calibrated by placing single-tone signal sources at different angles at equal intervals and analyzing the phase difference of received signals.

Description

Technical Field

[0001] The present invention relates to a non-uniform linear antenna array and a wide-band direction finding method thereof, belonging to the technical field of direction-of-arrival estimation in electromagnetic signal processing. Background Art

[0002] In recent years, with the rapid development of wireless communication technologies and the Internet of Things (IoT), the number of electromagnetic devices such as unmanned aerial vehicles and unmanned vehicles has increased rapidly. These unmanned electromagnetic devices have played an important role in fields such as logistics distribution, disaster relief, and emergency communication, and have become an important part of smart cities and the IoT. However, at the same time, illegal and unauthorized unmanned devices have also posed a threat to public safety. Therefore, it is very important to develop direction finding technologies for electromagnetic devices to timely detect the directions of electromagnetic devices in the environment.

[0003] Most of the antenna arrays used in existing direction finding technologies applied in actual engineering are uniform linear antenna arrays. To ensure high resolution in direction-of-arrival (DOA) estimation and avoid ambiguity in direction estimation, the element spacing is generally half of the wavelength of the target direction finding frequency band. This results in a too single frequency band in which the antenna array can operate in actual applications. If the target direction finding frequency band needs to be changed, the antenna configuration needs to be changed, which is very inconvenient. Some researchers have also proposed some non-uniform antenna array design methods, such as nested arrays and co-prime arrays, etc. However, the arrays targeted by these studies have a large number of array elements and are for theoretical research, lacking applications in actual environments. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art and propose a non-uniform linear antenna array and a wide-band direction finding method thereof. Aiming at the deficiencies of existing direction finding technologies, a non-uniform linear antenna array is designed so that some elements in the array can move. By means of the method of virtual elements, it can operate in a wide frequency band range, greatly improving the flexibility of the array and the frequency band range covered by the array. A calibration method for solving the phase deviation caused by the antenna pattern and the radio frequency channel is proposed. By placing single-tone signal sources at different equally spaced angles and analyzing the phase difference of the received signals, the deviation caused by the antenna pattern and the radio frequency channel is calibrated. In this way, the problems that the existing array cannot operate in a relatively wide frequency band range, the direction finding accuracy is affected by hardware conditions, and the accuracy is not high are solved.

[0005] The technical solution of the present invention is:

[0006] A non-uniform linear antenna array, which includes four array elements, namely array element array1, array element array2, array element array3, and array element array4;

[0007] Let the distance between array element array1 and array element array4 be d 14 , and d 14 is a fixed value;

[0008] The distance between array element array1 and array element array2 is d12’, the distance between array element array2 and array element array3 is d23’, and the distance between array element array3 and array element array4 is d34’;

[0009] The initial value of d12’ is d 12 , the initial value of d23’ is d 23 , and the initial value of d34’ is d 34 ;

[0010]

[0011] And the array element array2 in this non-uniform linear antenna array can move towards the direction of array element array1, and the moving distance is x1, and the maximum value of x1 is x 1max , the array element array3 can move towards the direction of array element array4, and the moving distance is x2, and the maximum value of x2 is x 2max .

[0012] A wide-band direction finding method for a non-uniform linear antenna array. The wide band refers to a frequency range of 300 MHz - 6 GHz. The non-uniform linear antenna array in the initial state composed of array element array1, array element array2, array element array3, and array element array4 is defined as the initial array D0;

[0013] The steps of this method include:

[0014] The first step is to move the distance x1 of the array element array2 in the initial array D0 towards the direction of array element array1 and the distance x2 of the array element array3 towards the direction of array element array4 according to the frequency point to be monitored, so as to obtain the intermediate array D1;

[0015] The second step is to perform phase calibration on the intermediate array D1 obtained in the first step;

[0016] Step 3: Generate virtual array elements based on the electromagnetic wave signals a1 received by array element array1, a2 received by array element array2, a3 received by array element array3, and a4 received by array element array4 in the intermediate array D1 after phase calibration in Step 2;

[0017] Step 4: Add the virtual array elements generated in Step 3 to the intermediate array D1 to generate a five-element array D2, and then remove the amplitude information from the array received data, retaining only the phase information;

[0018] Step 5: Calibrate the steering vector of the five-element array D2 generated in Step 4 using the phase difference of the antenna array obtained during phase calibration in Step 2;

[0019] Step 6: Use the five-element array D2 after steering vector calibration in Step 5 to measure the direction of the radiation source at the frequency point to be monitored.

[0020] In the first step, the methods for determining the distances x1 and x2 are as follows:

[0021] Let the frequency point to be monitored be f, c is the electromagnetic wave speed;

[0022] If Then x2 = 0;

[0023] If Then x1 = 0,

[0024] If Then x1 = 0, x2 = 0;

[0025] If Then x2 = 0;

[0026] If Then x1 = x 1max ,

[0027] If Then x2 = 0;

[0028] If Then x1 = x 1max ,

[0029] If Then x2 = 0;

[0030] If Then x1 = x 1max ,

[0031] In the second step, the method for phase calibration of the intermediate array D1 is as follows:

[0032] Step 21: Place a single-tone signal radiation source at a position d away from the intermediate array D1, determine the set of incident angles of the radiation source θ = [θ1, θ2,..., θ n , where n is the number of positions where the radiation source is placed. Transmit a single-tone signal through the single-tone signal radiation source, use the intermediate array D1 to receive the signal, and calculate the phase difference between element array1 and element array2 in the intermediate array D1;

[0033] Step 22: Change the transmission angle of the single-tone signal transmitted by the single-tone signal radiation source in Step 21 to obtain the phase difference between element array1 and element array2 in the intermediate array D1 at different transmission angles;

[0034] Step 23: Fit the phase differences between element array1 and element array2 in the intermediate array D1 at different angles and different angles to obtain a function curve with the abscissa being the transmission angle θ and the ordinate being the phase difference Δφ els,12 (θ), which is marked as curve L 12 ;

[0035] Using the same method, obtain curve L between element array1 and element array3 13 , where the abscissa is the transmission angle θ and the ordinate is the phase difference Δφ els,13 (θ) function curve;

[0036] Using the same method, obtain curve L between element array1 and element array4 14 , where the abscissa is the transmission angle θ and the ordinate is the phase difference Δφ els,14 (θ) function curve;

[0037] In Step 21, the formula for calculating the phase difference is:

[0038] The signal received by element array1 is:

[0039] a1 = r I1 [n] + jr q1 [n]

[0040] The signal received by element array2 is:

[0041] a2 = r I2 [n] + jr Q2 [n]

[0042] The signal received by array element array3 is:

[0043] a3 = r I3 [n] + jr Q3 [n]

[0044] The signal received by array element array4 is:

[0045] a4 = r I4 [n] + jr Q4 [n]

[0046] n = 0, 1,..., L - 1

[0047] where j is the imaginary unit;

[0048] r I1 [n] is the I-channel signal received by array element array1, r Q1 [n] is the Q-channel signal received by array element array1;

[0049] r I2 [n] is the I-channel signal received by array element array2, r Q2 [n] is the Q-channel signal received by array element array2;

[0050] r I3 [n] is the I-channel signal received by array element array3, r Q3 [n] is the Q-channel signal received by array element array3;

[0051] r I4 [n] is the I-channel signal received by array element array4, r Q4 [n] is the Q-channel signal received by array element array4;

[0052] L represents the length of the received signal;

[0053] The phase difference between array element array1 and array element array2 is:

[0054]

[0055] The phase difference between array element array1 and array element array3 is:

[0056]

[0057] The phase difference between array element array1 and array element array4 is:

[0058]

[0059] In the third step, the generated virtual array element is arrayvir , the corresponding signal is a vir , and the steering vector is A vir , specifically:

[0060] If then

[0061] If then

[0062] If then

[0063] If then

[0064] If then

[0065] If then

[0066] If then

[0067] If then

[0068] If then

[0069] In the fourth step described above, the generated five-element array D2 is:

[0070] [a1, a2, a3, a4, a vir

[0071] The electromagnetic data after removing the amplitude information is:

[0072]

[0073] Among them, is the electromagnetic data of the array element array1 after removing the amplitude information;

[0074] is the electromagnetic data of the array element array2 after removing the amplitude information;

[0075] is the electromagnetic data of the array element array3 after removing the amplitude information;

[0076] is the electromagnetic data of the array element array4 after removing the amplitude information; ​

[0077] The electromagnetic data after removing the amplitude information for the virtual array elements;

[0078] angle(·) is the operation of taking the angle of a complex number;

[0079] In the fifth step, the steering vector of the five-element array D2 after calibration is A(θ);

[0080]

[0081] Advantageous effects

[0082] 1. The present invention proposes a design method for a non-uniform array covering a wide frequency band of half wavelength, enabling some array elements to be movable. By means of the virtual array element method, the flexibility of the array and the frequency band range covered by the array are greatly improved.

[0083] 2. The present invention proposes a calibration method for solving the phase deviation caused by the antenna pattern and the radio frequency channel. By placing single-tone signal sources at different equally spaced angles and analyzing the phase difference of the received signals, the deviation caused by the antenna pattern and the radio frequency channel is calibrated.

[0084] 3. The present invention generates virtual array data based on the actual array received data and uses it together with the actual received data as the input of the algorithm. A one-dimensional virtual array component is added to the steering vector, and at the same time, the amplitude information of the input data is removed, only the phase information is retained, so as to achieve accurate direction estimation. Brief description of the drawings

[0085] Figure 1 Schematic diagram of the four-antenna array design;

[0086] Figure 2 Schematic diagram of the measurement experiment;

[0087] Figure 3 Schematic diagram of generating virtual array elements;

[0088] Figure 4 Deviation caused by the antenna pattern and the radio frequency channel;

[0089] Figure 5 Schematic diagram of the direction finding result. Specific implementation manners

[0090] The present invention will be further described below with reference to the drawings and embodiments.

[0091] Embodiment

[0092] As Figure 1 、 Figure 2 And Figure 3As shown, a non-uniform linear antenna array, the non-uniform linear antenna array includes four array elements, namely array element array1, array element array2, array element array3, and array element array4;

[0093] Let the distance between array element array1 and array element array4 be d 14 and d 14 be a fixed value;

[0094] The distance between array element array1 and array element array2 is d12’, the distance between array element array2 and array element array3 is d23’, and the distance between array element array3 and array element array4 is d34’;

[0095] The initial value of d12’ is d 12 and the initial value of d23’ is d 23 and the initial value of d34’ is d 34 ;

[0096]

[0097] And the array element array2 in the non-uniform linear antenna array can move towards the direction of array element array1, the moving distance is x1, and the maximum value of x1 is x 1max and the array element array3 can move towards the direction of array element array4, the moving distance is x2, and the maximum value of x2 is x 2max .

[0098] A wide-band direction finding method for a non-uniform linear antenna array, the wide band refers to a frequency range of 300 MHz - 6 GHz, and the non-uniform linear antenna array in the initial state composed of array element array1, array element array2, array element array3, and array element array4 is called the initial array D0; the steps of this method include:

[0099] The first step: According to the frequency point to be monitored, move the distance x1 of the array element array2 in the initial array D0 towards the direction of array element array1, and move the distance x2 of the array element array3 towards the direction of array element array4 to obtain the intermediate array D1;

[0100] The distance between array element array1 and array element array4 is d 14 = 0.66 m, which is a fixed value, x 1max = 0.1 m, x 2max = 0.1 m;

[0101] The initial value d of d12’ 12 and the initial value d of d23’23 , the initial value d of d34’ 34 are respectively:

[0102]

[0103] The frequency point to be monitored is f = 2.4 GHz,

[0104] then x1 = x 1max = 0.1,

[0105] Therefore, move the element array2 in the initial array D0 towards the element array1 by a distance of 0.1 m, and move the element array3 towards the element array4 by a distance of 0.0375 m to obtain the intermediate array D1;

[0106] Second step, perform phase calibration on the intermediate array D1 obtained in the first step;

[0107] Step 21, place a single-tone signal radiation source at a position d = 10 m away from the intermediate array D1, and determine the set of incident angles of the radiation source Emit a single-tone signal through the single-tone signal radiation source, use the intermediate array D1 to receive the signal, and calculate the phase difference between the element array1 and the element array2 in the intermediate array D1

[0108] Step 22, change the emission angle of the single-tone signal emitted by the single-tone signal radiation source in Step 21 to obtain the phase difference between the element array1 and the element array2 in the intermediate array D1 at different emission angles;

[0109] Step 23, fit the phase differences between the element array1 and the element array2 in the intermediate array D1 at different angles and different angles to obtain a function curve L with the emission angle θ as the abscissa and the phase difference Δφ els,12 (θ) as the ordinate 12 :

[0110]

[0111] Using the same method, obtain the curve L between the element array1 and the element array3 13 :

[0112]

[0113] wherein, the abscissa is the emission angle θ and the ordinate is the function curve of the phase difference Δφ els,13 (θ);

[0114] Using the same method, the curve L between the array element array1 and the array element array4 is obtained 14 :

[0115]

[0116] where the abscissa is the emission angle θ and the ordinate is the phase difference Δφ els,14 (θ); the function curve

[0117] The curve L obtained by fitting 12 , L 13 , L 14 As Figure 4 shown

[0118] In the third step, according to the electromagnetic wave signals a1 received by the array element array1, a2 received by the array element array2, a3 received by the array element array3, and a4 received by the array element array4 in the intermediate array D1 after phase calibration in the second step, a virtual array element is generated

[0119] The generated virtual array element is array vir , and the corresponding signal is a vir , and the steering vector is A vir , specifically:

[0120] Then

[0121] In the fourth step, the virtual array element generated in the third step is added to the intermediate array D1 to generate a five-element array D2

[0122] The five-element array D2 is The electromagnetic data after removing the amplitude information in the generated five-element array D2 is:

[0123]

[0124] In the fifth step, the phase difference of the antenna array obtained during phase calibration in the second step is used to calibrate the steering vector of the five-element array D2 generated in the fourth step

[0125] After calibration, the steering vector of the five-element array D2 is A(θ);

[0126]

[0127] In the sixth step, the five-element array D2 after steering vector calibration in the fifth step is used to measure the direction of the radiation source at the frequency point to be monitored, and the measurement result is as Figure 5 shown

[0128] In summary, the above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A non-uniform linear antenna array, characterized in that: The non-uniform linear antenna array includes four array elements, namely array element array1, array element array2, array element array3, and array element array4; Let the distance between array element array1 and array element array4 be d 14 , and d 14 is a fixed value; Let the distance between array element array1 and array element array2 be d12’, the distance between array element array2 and array element array3 be d23’, and the distance between array element array3 and array element array4 be d34’; The initial value of d12’ is d 12 , the initial value of d23’ is d 23 , the initial value of d34’ is d 34 ; Moreover, the element array2 in the non-uniform linear antenna array can move towards the direction of the element array1, and the moving distance is x1, and the maximum value of x1 is the set threshold x 1max , the element array3 can move towards the direction of the element array4, and the moving distance is x2, and the maximum value of x2 is the set threshold x 2max .

2. A wide-band direction finding method for a non-uniform linear antenna array, characterized in that: The wide band refers to a frequency range of 300 MHz - 6 GHz. The non-uniform linear antenna array in the initial state composed of array element array1, array element array2, array element array3, and array element array4 is called the initial array D0; The steps of this method include: The first step, according to the frequency point to be monitored, move the array element array2 in the direction of array element array1 by a distance x1, and move the array element array3 in the direction of array element array4 by a distance x2 in the initial array D0, to obtain the intermediate array D1; The second step, perform phase calibration on the intermediate array D1 obtained in the first step; The third step, generate virtual array elements according to the electromagnetic wave signals a1 received by array element array1, a2 received by array element array2, a3 received by array element array3, and a4 received by array element array4 in the intermediate array D1 after phase calibration in the second step; The fourth step, add the virtual array elements generated in the third step to the intermediate array D1 to generate a five-element array D2, and then remove the amplitude information in the received data, only retaining the phase information; The fifth step, use the phase difference of the antenna array obtained when performing phase calibration in the second step to calibrate the steering vector of the five-element array D2 generated in the fourth step; The sixth step, use the five-element array D2 after steering vector calibration in the fifth step to measure the direction of the radiation source at the frequency point to be monitored.

3. A wide-band direction finding method for a non-uniform linear antenna array according to claim 2, characterized in that: In the first step, the determination method of the distance x1 and the distance x2 is: Let the frequency point to be monitored be f, where c is the speed of electromagnetic waves; If then x2 = 0; If then x1 = 0, If then x1 = 0 and x2 = 0; If then x2 = 0; If then x1 = x 1max , If then x2 = 0; If then x1 = x 1max , If then x2 = 0; If then x1 = x 1max , 4. A wide-band direction finding method for a non-uniform linear antenna array according to claim 3, characterized in that: In the second step, the method for performing phase calibration on the intermediate array D1 is: Step 21, place a single-tone signal radiation source at a position d away from the middle array D1, determine the set of incident angles of the radiation source θ = [θ1, θ2,..., θ n , where n is the number of positions where the radiation source is placed. Transmit a single-tone signal through the single-tone signal radiation source, use the middle array D1 to receive the signal, and calculate the phase difference between the array element array1 and the array element array2 in the middle array D1; Step 22, change the emission angle of the single-tone signal emitted by the single-tone signal radiation source in step 21 to obtain the phase difference between array element array1 and array element array2 in the intermediate array D1 at different emission angles; Step 23, fit the phase differences between the array elements array1 and array2 in the intermediate array D1 at different angles and under different angles, and obtain a function curve with the emission angle θ as the abscissa and the phase difference Δφ els，12 (θ) as the ordinate, marked as curve L 12 ; Using the same method, the curve L between the array element array1 and the array element array3 is obtained 13 , where the abscissa is the emission angle θ and the ordinate is the phase difference Δφ els，13 (θ); the function curve Using the same method, the curve L between the array element array1 and the array element array4 is obtained 14 , where the abscissa is the emission angle θ and the ordinate is the phase difference Δφ els，14 (θ) function curve.

5. A wide-band direction finding method for a non-uniform linear antenna array according to claim 4, characterized in that: In step 21, the formula for calculating the phase difference is: The signal received by array element array1 is: a1 = r I1 [n] + jr Q1 [n] The signal received by array element array2 is: a2 = r I2 [n] + jr Q2 [n] The signal received by array element array3 is: a3 = r I3 [n] + jr Q3 [n] The signal received by array element array4 is: a4 = r I4 [n] + jr Q4 [n] n = 0, 1,..., L - 1 where j is the imaginary unit; r I1 [n] is the I-channel signal received by array element array1, r Q1 [n] is the Q-channel signal received by array element array1; r I2 [n] is the I-channel signal received by array element array2, r Q2 [n] is the Q-channel signal received by array element array2; r I3 [n] is the I-channel signal received by array element array3, r Q3 [n] is the Q-channel signal received by array element array3; r I4 [n] is the I-channel signal received by array element array4, r Q4 [n] is the Q-channel signal received by array element array4; l represents the length of the received signal.

6. A wideband direction finding method for a non-uniform linear antenna array according to claim 5, characterized in that: The phase difference between array element array1 and array element array2 is: The phase difference between array element array1 and array element array3 is: The phase difference between array element array1 and array element array4 is:

7. A wideband direction finding method for a non-uniform linear antenna array according to claim 4, characterized in that: In the third step described above, the generated virtual array element is array vir , and the corresponding signal is a vir , and the steering vector is A vir , specifically: If then If then If then If then If then If then If then If then If then 8. A wideband direction finding method for a non-uniform linear antenna array according to claim 4, characterized in that: In the fourth step, the generated five-element array D2 is: [a1, a2, a3, a4, a vir ​ The electromagnetic data after removing the amplitude information is: Among them, is the electromagnetic data after removing the amplitude information of the array element array1; The electromagnetic data after removing the amplitude information for array element array2; The electromagnetic data after removing the amplitude information for array element array3; The electromagnetic data after removing the amplitude information from array element array4; The electromagnetic data after removing the amplitude information for the virtual array elements; angle(·) is the operation of taking the angle of a complex number.

9. A wideband direction finding method for a non-uniform linear antenna array according to claim 4, characterized in that: In the fifth step, the steering vector of the five-element array D2 after calibration is A(θ);

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